1. Field of the Invention
The present invention relates to an electromagnetic clutch that transmits and cuts rotational power and that is particularly suitable for driving a compressor for an automobile air conditioning apparatus.
2. Description of Related Art
One type of known electromagnetic clutch for a compressor is disclosed in JP-U-6-30535. The electromagnetic clutch has a rotor which is driven by a driving source such as an engine and has an armature which is disposed opposite the rotor keeping a predetermined small gap between them. The armature is supported by a hub of the driven side via a leaf spring.
When an electromagnetic coil is energized to generate an electromagnetic attractive force, the armature is attracted to the rotor, and the armature is attached to the rotor by an elastic deformation of the leaf spring. Consequently, the rotation of the rotor is transmitted to the driven-side hub via the armature and the leaf spring, and a compressor connected to the hub is operated.
However, according to the above described electromagnetic clutch, a triangle-shaped flange portion, extended outwardly in the radial direction, is unitarily formed with the driven-side hub. One ends of a plurality of the leaf springs (for example, three leaf springs) are connected to the flange portion, and the other ends of the leaf springs are connected to the armature.
Accordingly, in an axial direction of the electromagnetic clutch, the flange portion of the driven-side hub is piled up on the leaf spring as well as the armature is piled up on the leaf spring. Consequently, the electromagnetic clutch is increase in size in the axial direction, and the mounting performance of the electromagnetic clutch on a limited space such as an engine compartment is decreased.
Furthermore, since a plurality of leaf springs are used, the assembly of the leaf springs are complicated, thereby increasing the manufacturing cost of the electromagnetic clutch.